Heat treated glass fabric



Aug. 26, 1952 C, STRAKA 2,608,499

HEAT-TREATED GLASS FABRIC Filed sept. 12, 1946 ,BY @(1/- lI ATT NEY Patented ug. 26,.1'952: i l l ,UNITED STATES PATENT OFFICE HEAT TREATED GLASS FABRICv 1 T Cyril .I. .Straka, Wilkinsburg,n Pa., assignor` `to T Westinghouse Electric Corporation, East vPittsburgh, Pa., a corporation of `lennsylvania Application September 12, 1`9i6,`S`erial`No. 6965591 f 5 claims. Y (01."1544-43) 'I'his `invention relates toT composite members a heattreatedglass berV materialivhichza embodying glassriiber material and organo-silipreviouslyapplied `organic lubricantkhas been' con oxide resins applied thereto. Volatilized and carbonized by heat treatment in `TIn manufacturingglass fiber materials, it has thepresence of `a coating of a fluid phenylf'methyl been found necessary to apply organic lubricants, 5- siloxane.` T f T' :1 such as oils or starch, in an amount of 1% or less A stillfurther object of the invention is .to pro'-L of the glass material to the glass laments as videgcomposite` material' composed ofi a phenyl they are drawn out. A great number of laments, methyl Siloxane and a glass ber material derived usually 102, are combined to form a glass ber or by applying a 'minor amount `o1` phenyl methyl thread and the presenceV of a. lubricant is necessiloxane `to glass fiber material containinganorf,

sary in order to prevent the llaments from cutganclubri'cant and heat treatrlgtheCoatediglass ting one another and to permit relative motion of fiber material tovolatilize and; carbonize the or`v the *filaments as the fibers are bent and distorted ganic lubricant.- duringT subsequent processing. The glass fila-` Other objects of the inventionwvill :inpartbe ments are highly abrasive and relatively adherent obvious and will in part` appear hereinafter. For4 to one another' so that without the lubricant the amfuller `understanding of the naturegandfobjects threads could not be successfully spun and woven. of the invention, reference Should be had t0.` the A relatively small amount ofToil,` starch` or the iollowingfdetailed description and drawing, in like organic hydrocarbon-oxygen compound is which;` i l A 'l present, but substantially the entire surface of the Eigure `1 isa schematic vievv inj elevation,` partlyA glass'filaments is covered with a` thin layer of the insectomoi anapparatus fOr heat treating glass,

organic material.` ber material; T T T Itis highly desirable to combine glass ber ma- Fig. 2irs a View in perspective of a slot cell' terial with organo-silicon oxide resins in order lnergand j EL Y g T j to secure members capable of use at elevated tem`' 25 Fig. 3` isA a view-,irl perspective, partlyingjc ssj peratures while having good tensile Strength and Sctiomoi a laminated jirlerrlbr` 1 other physical4 and e1eotrica1 propertieaTTT It has T It has been discovered that several unexpected; been discovered, however, that due to the presence advantages occur when a glass fiber materia-LT of the organic lubricants .on the glass materials SllQh as glaS CIO'DhrglaSS braid, kntedglassfah-g that the bonding of the organo-silicon oxide rios and the ike,-carryng an Organic lubricant` resinslto the glass is" relatively unsatisfactory. applied duringtheprocessor` previous manufa The presence' of an intermediate layer of the ture and then coated with a iuidphenyl meth l.

Starch or oil further results in poor dielectric SlXSn arl amimt `equal to from about 5%; strength; 10W moisture resistance and other det0 15% 0f the Weght'f'lh glaSSlflbBr-materalfis cienc-ies in a composite material prepared from burnedr heat treiliel` al? 2i temprature and-f r the glass `materials and the organo-silicon oxide a Sufeht PerOd of time to volatilizeTand-lca 4T' resins, l T bonizethe organiclubricant. '.'lhe lglassmaterial While it has been proposed to subject woven so produced maybe used diret1yor"`tie heat, glass clothor other glass ber material to temtreated `glass "lerfmatell C"tlryllgf the -lli-T peratures suflicient to burn oir the organic lubriphenyl methyl SlOXarle COMIITIELY be. treatedi cant on Tthe glass, previous to applying resins 40 With additional lOymeIZableDheriylrrrithyl'silf thereto, it has been found that the improvement Olgarle, aridTmemberS produ'ed herfrlr bySubso Aproduced is meager and certain undesirable jeolngA the" additional j" siloxane coatirigj o'ritlie4 features result. For example, the bond strengthl glafSS `fiber material t0' POlymerZirlg liratrl il.; of the organo-silicon oxide resin to the glass The improvement inthe composite malrpr -n bers is low when applied to heat treated glass dlledaCCOrding SQ the invention is substant 1fbermaterial; 'T and resultsV inproducts `having properties. t. The object Tofthis invention is to provide for avallableheretfr. heat treating glassfiber material carrying an or- Referring t0 Fig. `1 of` thedrawing, ther ganic lubricant and a 'superimposed coating of a llisralledjan f apparatus fOr' heal? treatin glass? huid phenyl methyl siloxane or a huid siloxane fiber materialn' accordanceiwith the invention.' composed of phenyl methyl siloxane admixed Glass bermateriall, such, for example, asglass. with other organo-silicon oxides, at a temperature Cloth coated" with an organic lubricant, suchfasj and for atime Sufficient to volatilize and to cara vegetable oil or starch or the like, passesover bonizeltheorganie lubricant.L `T rollers l2 and `I4 where it coatedin thetanlrr `:Afurther(moet of the inventionis to' provide 55 is with a mia phenyl methyl snoxane- "lsniy merizable to a solid resinous state. The phenyl methyl siloxane I8 may be a solution composed of a siloxane having various ratios of R to Si and various proportions of the phenyl to methyl groups thereon dissolved in an organic solvent, such as toluene, or it may be a low polymeric phenyl methyl siloxane of a low viscosity. The glass fabric I ll coated with theifluid phenyl methyl siloxane emerges from the bath and passes over a roller 20 cooperating with a doctor blade 2| or other wiping means for maintaining a predeter mined amount of the fluid phenyl methyl siloggane on the glass cloth.

In practice it has been found that best results are secured when the amount of phenyl methyl siloxane present in the glass cloth varies from about 5% to 15% of the weight of th? glass cloth. A substantially greater amount ofthe siloxane results in blistering during subsequent heat treatment. If substantially less than 5% of phenyl methyl siloxane is present, the advantages of. theinvention are not attained.

.'rThesiloXane treated glass cloth I0 then passes thr'oughl anoven 2'2 provided with a heating element 24 wherein a temperature of from about 300" C. .to .456."k C., or lslightly higher, is maintained in order to volatilize and to carbonize the organic lubricant present on the glassicloth. At 350310. an 'exposure of three minutes for two mil glass cloth is' sufcient to eliminate the organic lubricant. For higher temperatures the heating interval may be made proportionately shorter. The time of heat-treatment mayA be "somewhat longer but Vshould not be so long as to decompose toany substantial degree the siloxane. The fluid phenyl 'methyl siloxane cures vduring the heat treatment to'a tack-free solid resinous state. Obviously "a gas burner orv other suitable source of heat may be employed in the oven 22;*"lihe glass cloth will be found-to be 'much smoother after theheatA treatment. Thereafter, the glass cloth passes overguide rolls 26 and 28` and may be wound up intol a roll 30 'for a subsequent use.

For coating the glass fiber material Vprior to he'at'tre'atment, any of a variety of phenyl methyl siloxanes has been found satisfactory. `For Vexample, a phenyl methyl siloXane having a ratio ofRto Si'o'f 2 wherein one-third'of the Rs are phenylv groups gavel excellent results. The vis'-V co'sit'y'of different fluids of this class used "with success varied in; viscosity from 50 to 75* centisftokejs. In another case a phenyl methyl silex- Erie having RV toVv Si. ratio f 1.5 and having a substantiallyequal number o f phenyl and methyl groupswas 'employed successfully. In still 'an--y other case the phenyl methyl siloxane had anR toi'Si' ratio of 1.2 and lcontaining a` substantially equal number of'phenyl Vand methyl groups was applied'to the glass cloth vwith similarly v's'atisf factory', results. On the other hand, the use. of. dimethyl' sloxane did not produce. satisfactory results 'onjheat treatment. 4It isv believedY that during the 'heat treatment, thephenyl methyl 'sfilqxane undergoes some. chemical and physical changes concurrently' with the carbonization and velatilization'of organic lubricant whereby the phenyl' 'methyl siloxane penetrates into. the in terstices. of each berand furthermore adheres tpeachglass `filament in a manner not obtainable if itjwere. applied after. heat treatment.

B Qrjsfome applications the heat treated glass.

material carrying from about to 15% of its weightibf 'phenyl methyl siloxane may be used out additional treatment. Ihe pores and .-heatftreated glass fiber material.

4 to Warrant use of the material as insulating tape or cloth.

The heat treated glass fiber material may be coated with additional phenyl methyl siloxane, either similar to that originally applied or different therefrom, capable of being polymerized to a resinous state. The amount and kind of additional Aphenyl methyl siloxane applied will depend upon the requirements for the resulting composite material. For producing sheet material for electrical insulating applications, for instance, as slot cell liners and conductor wrapping, from '20% to 59% by weight or more of phenyl methyl siloxane may be applied to the This amount of phenyl methyl siloxane is not only suflicient to completelyimpregnate the glass fiber sheet and produce a pore-free, smooth surfaced, product but will provide a surface coating imparting more rigidity.

.Glass @10th of two mil thickness treatediwiih 1.0% bym/.eight @fa luidphenyl h- Yl having an R to .Si ratio of. .1.5. and Cantal .s substantially equal number of phenyl andmethyl groupsV was heat treated for three minutes-at 380 C. The material was then coated t@ plainly thereto an additional quantity o fthe saine. Sloi: ane equal to to 35% of the weight, 0.1. the, bien@ treated glass cloth. The coated vglassiber mate-f rial wasthen cured at a temperature. of 3599' until ythe siloxanehad'been converted to a solid resin. Glass cloth ofa similar k-ind but. heat treated without an initialcoating vof anyphenyl methyl siloXane was coated to. provide similar total Weight of phenyl .methyl siloxane under- Lthe same heat treating conditions. Tests indicated the following improvement of the. former as com-.- pared to the latter:

Topp. 1 Y. .i .4 .1'.

Tipi. 0f Glaifabiie Dielectric .Strength (volts per mil);-.

Short Tim'eMe'thodz" 'MU Dia.. Electrodes- 1,875: l .2,796 2 Dia. Electrodesg1, 195iY 1,5412 Conditionof treated: materiell Bough Snipqtli GAO 'L"ticegfqitnecipui white mieu sufncienuy Ii. will be apparent f rpipfihp. liable ihiitaaiipf. pipi/ement in dielectric Strength of appppiima.. 1y.- 50-%5 was.. obtained; by: emplpyipaf glass @het material prepppitpdv with .iliefsilOXa-pe. @pippe he i treatment as. Compared t9; theliat, .t ea up; coated, glass fibel maflf. .Ellleil'limo condition of the treated material of this i vene lacking a precoatingof.siloxanebeforeheattreata ment,

The heat treated.4 glass. liber. i sheet. materiali Vof this invention may belcoatedfavnumherxoff'times with a phenylmethylsiloxane.withccuringeof the sloxane betwensuccessive applications. Thus, in one case three milglass `fiber sheet initially coatedywith a phenyl methyl siloxane and heat treated to remove the organic lubricant was coated -rthree times in a toluene solution of a phenyl methyl siloxane having an R to Si ratio of 1.2, the phenyl and methyl groups being substantially equal in number and the toluene solution containing approximately 40% siloxane solids. After three applications ofthe phenyl methyl siloxane with heat treatment afterv each successive applicatlonat altemperature `of from 320 to 380 C. for `three minutes; `the i thickness of the sheet` was approximately `seven mils. This sheet was fairly rigid and Was capable of use as a support, a slot cell liner or in other applications requiring a relatively rigid insulating member.

The heat treated glass fiber material of this invention is particularly suitable for the preparation of laminated members for high temperature use. Referring to Fig. 3 of the drawings, there is illustrated a laminated member 50 composed of a plurality of sheets I0 of glass cloth coated with phenyl methyl siloxane resin. A laminate similar to that shown in Fig. 3 was prepared by applying to phenyl methyl siloxane precoated seven mil thick glass cloth and heat treated to remove the organic lubricant sufficient of a solution of a phenyl methyl siloxane having an R to Si ratio of from l. to 1.2 in an amount approximately equal to the weight of the glass cloth. The coated glass fiber cloth was dried by `moderate heating in order to remove the solvent vglass cloth with the solvent-free siloxane resin were superimposed and subjected to a pressure of 1000 pounds per square inch at a temperature of 200 C. for one hour. A laminated member of high bond strength was produced. Comparative tests for one-half inch thick laminates show that the bond strength of laminates produced from phenyl methyl siloxane and the heat treated glass cloth of this invention was approximately 1100 pounds. The bond strength of laminates employing glass cloth that was heat treated without a siloxane precoating, but otherwise identical with the former material, was only 700 pounds,

It will be apparent accordingly that the precoating of glass fiber materials with a phenyl methyl siloxane before heat treatment to drive off organic lubricant from the glass fiber material results in a great improvement in the characteristics of the composite material produced from the glass cloth and subsequently applied phenyl methyl siloxane resins.

A minor proportion of a compatible organosilicon oxide may be present in the phenyl methyl siloxane. Phenyl ethyl siloxanes in small amounts, for instance, may be admixed therein. For most purposes, however, the phenyl methyl siloxanes alone are preferred. Catalysts such as cobalt naphthenate, lead resinate and the like may be added to expedite curing of the siloxane. Small amounts of mica dust, silica or other inorganic ller may be present in the siloxane to impart a desired viscosity.

Since certain obvious changes may be made in the above procedure and different embodiments of the invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. The process of treating a glass ber material carrying an application of ,organic `,hydrocarbon-'I oxygenlubricant, comprising applying atcoating ofliquid phenyl methyl siloxaneto the glasslfiber material in an amount equal to from about' 51%` to 15% of the` weight of glass bers and heatwtreating thecoated glass ibermaterial ata tempera;- ture of from about 300 C; to about `450C. toria sufficient period of .time to volatilize and carbonize the organic lubricant but not sufficient to deteriorate the phenyl methyl siloxane to any significant amount, Athe time being inversely .proportional to the temperature, and the timebeing of the order of three minutes at a temperature of from 320 C. to 380 C.

2. The process of treating a glass liber material carrying an application of organic hydrocarbonoxygen lubricant, comprising applying a coating of liquid phenyl methyl siloxane to the glass ber material in an amount equal to from about 5% to 15% of the Weight of glass fibers, heat treating the coated glass ber material at a temperature of from about 300 C. to about 450 C. for a sufficient period of time to volatilize and carbonize the organic lubricant but not sufiicient to deteriorate the phenyl methyl siloxane to a signicant amount, the time being inversely proportional to the temperature, and the time being of the order of three minutes at a temperature of from 320 C. to 380 C., applying an additional coating of a iiuid polymerizable phenyl methyl siloxane and polymerizing the phenyl methyl siloxane to the solid state.

3. Sheet material comprising, in combination, a sheet of glass bers, the glass fibers having been originally coated with an organic hydrocarbonoxygen lubricant, subsequently coated with from 5% to 15% by weight of a liquid phenyl methyl siloxane and then heat treated to volatilize and carbonize the organic lubricant without materially deteriorating the applied siloxane, the time of heat treatment being inversely proportional to the temperature, the time being of the order of three minutes for a temperature of from 320 C. to 380 C., the heat treatment temperatures being from about 300 C. to 450 C.

4. Sheet material comprising, in combination, a sheet of glass fibers, the glass bers having been originally coated with an organic hydrocarbonoxygen lubricant, subsequently coated with from 5% to 15% by Weight of a liquid phenyl methyl siloxane and then heat treated to volatilize and carbonize the organic lubricant, without materially deteriorating the` applied siloxane the time of heat treatment being inversely proportional to the temperature, the time being of the order of three minutes for a temperature of from 320 C. to 380 C., the heat treatment temperatures being from about 300 C. to 450 C. and additional phenyl methyl siloxane resin in a polymerized condition applied to and impregnating the glass fibers, the resulting sheet material being smoother and having a substantially higher dielectric strength than the same material heattreated Without a coating of siloxane present With the lubricant.

5. A high bond strength laminate comprising, in combination, a plurality of sheets of glass bers, the sheets of glass fibers derived by applying to glass fibers coated with an organic hydrocarbon-oxygen lubricant a coating of a liquid phenyl methyl siloxane in an amount equal to from 5% to 15% of the weight of the sheets, and heat treating the glass bers so coated at a temperature of from 300 C. to 450 C. for a period of time suiiicient to volatilize and carbonize the 7, organic lubricant, the time'being inverselyv pro- I UNITED STATES PATENTS portonal to the temperature, and the time being 'Number Name Date.: of the order of three minutes at. a temperature 2 225,009 Hyde Dec. 17 1940 of frem320 C; to 380'C., and additional amounts 2:258213 Rochow ,Oct 7 1941 ofi-a polymerizedv phenyl methyl siloxane applied 5 2,258,222 Rochow, Oct 7 1941 t0 the Sheets of: glassbers to impregnate and to 2,386,466 Hyde Oct'. 9 1945 bonlintO the laminate. Hyde Dc. 4) l CYRIL J STRAKA 2,392,805 Biefeid Jan. 15, 1946 REFERENCES CITED lo OTHER REFERENCES v The following references are of record inthe Silicone Resin Bonded Lamnates, article by lerpf this patent; Larsen et al. in Modern Plastics, vol. 23, No. 7,

published March 1946, pages 1GO-'162, 192, 194. 

5. A HIGH BOND STRENGTH LAMINATE COMPRISING, IN COMBINATION, A PLURALITY OF SHEETS OF GLASS FIBERS, THE SHEETS OF GLASS FIBERS DERIVED BY APPLYING TO GLASS FIBERS COATED WITH AN ORGANIC HYDROCARBON-OXYGEN LUBRICANT A COATING OF A LIQUID PHENYL METHYL SILOXANE IN AN AMOUNT EQUAL TO FROM 5% TO 15% OF THE WEIGHT OF THE SHEETS, AND HEAT TREATING THE GLASS FIBERS SO COATED AT A TEMPERATURE OF FROM 300* C. TO 450* C. FOR A PERIOD OF TIME SUFFICIENT TO VOLATILIZE AND CARBONIZE THE ORGANIC LUBRICANT, THE TIME BEING INVERSELY PROPORTIONAL TO THE TEMPERATURE, AND THE TIME BEING OF THE ORDER OF THREE MNUTES AT A TEMPERATURE OF FROM 320* C. 380* C., AND ADDITIONAL AMOUNTS OF A POLYMERIZED PHENYL METHYL SILOXANE APPLIED TO THE SHEETS OF GLASS FIBERS TO IMPREGNATE AND TO BOND THEM INTO THE LAMINATE. 